Threshold. The Gemini Project, #1

Five years ago, her father died. Five minutes ago, he reappeared in her bedroom. Five seconds ago, a helicopter landed on her roof. Fifteen-year-old Maddie Harris has spent five years learning to live without her father. But when he appears in her room and whispers, "I'm sorry, " before armed men drag them both away, her grief transforms into something far more dangerous: hope. Kidnapped and interrogated about a classified project she's never heard of, fifteen-year-old Maddie barely escapes with the help of an FBI agent who may not be on her side.
When a mysterious package arrives containing a device that shouldn't exist, Maddie realizes everything she thought she knew about his supposed death was a lie. As a powerful, secretive organization known as Project Gemini closes in, Maddie races to uncover the truth about her father's disappearance and the device anyone would kill to have. Every choice she makes carries consequences. Every secret she uncovers makes her a bigger target.
Because if she's captured-and the device falls into the wrong hands-her father's sacrifice will mean nothing. Some truths are more dangerous than lies. Some technologies should never see the light of day. And once you cross the threshold, there's no turning back.